Simplification of the instantiation of Service objects in the
generated sample file by removing the SoapClient options parameter. By
default, the cache_wsdl is disabled, the wsdl_url is set with the WSDL
url used to generate the package and trace is set with true. The
VALUE_WSDL_URL constant has been added to the generated WsdlClass
defined with the WSDL url used to generate the package.

Remove trailing ?> in generator files/classes.

Add WsdlToPhpGenerator::getWsdl($_index) method to get any WSDL at any
position.

Enhance generated sample file with explanation about the optional
parameter allowing to override the SoapClient Options. Remove the $wsdl
parareter previously used to instantiate each Service object.

Avoid Struct object to reset SoapClient when it is instantiated when
calling the parent constructor.
[UPDATE] several updates based on Github updated files
[UPDATE] minor updates
[UPDATE] code review and enhancements

Override WsdlToPhpModel::getOwner() method in inherited classes when it makes sense so the caller knows the exact return type

Enhanced attribute type definition by avoiding that the attribute type is the type of the class it belongs to
[UPDATE] global php doc harmonisation and minor improvement